docs: def dump(self, cache_file=None):
          """Write dump out to file `cache_file`, defaulting to
          ``self.cache_file``"""
          if cache_file is None:
              cache_file = self.cache_file
          if cache_file is not None:
              self.cache_file = cache_file
              with open(cache_file, 'wb') as pickle_fh:
                  pickle.dump(
                      (self.remote, self.backend.name, self.max_sleep_interval,
                       self.job_id, self._status, self.epilogue, self.ssh,
                       self.scp),
                      pickle_fh)